MotoGP rider Marco Simoncelli died exactly a week after Dan Wheldon, and while the tributes poured in for the 24-year-old following his death in Malaysia on Sunday there were calls to investigate the circumstances as the chairman of the Sepang circuit admitted safety in the sport could never be 100 per cent guaranteed.

The 24-year-old Italian lost control of his Honda at turn 11 four minutes into the race, but his bike regained partial grip and swerved across the track, straight into the path of American Colin Edwards and Valentino Rossi of Italy.While falling his helmet came off and Medical Director Michele Macchiagodena said that Simoncelli sustained "a very serious trauma to the head, to the neck and the chest" and died of his injures.It was the first fatality in MotoGP since Japan's Daijiro Katoh died from injuries sustained at the 2003 Japanese Grand Prix. Last year, however, Japanese teenager Shoya Tomizawa died after crashing in a Moto2 race at San Marino.Simoncelli's fatality raised the number of recorded deaths in MotoGP to 47 since it was founded in 1949.MotoGP race director Paul Butler pledged to investigate the circumstances surrounding the accident while Sepang circuit chairman Mokhzani Mahathir voiced his condolences and said it was unfortunate that a death occurred for the first time since the circuit opened in 1999.

"We had our standard operating procedure ... this is one-of-a-kind freak incident where the helmet came off and I am sure (motorcycling body) FIM and MotoGP will be looking into this," he said."It is a sad back-to-back weekend for motorsports. We try our best to avoid incidents and prepare for the worst. You see, 99 per cent of the time, riders falling and walking away. Only one per cent do not."You can never guarantee a 100 per cent safe race. You expose yourself to danger when you race. As professionals, they know MotoGP is dangerous. Believe it or not, that is what they live for. Our condolences to Marco. He will be missed dearly."Newly crowned MotoGP champion Casey Stoner said after the crash that he feared for Simoncelli. "As soon as I saw the footage it just makes you sick inside," the Australian said. "Whenever the helmet comes off that's not a good sign."Last season's MotoGP world champion Jorge Lorenzo recently suffered a serious injury which could have cost him a finger, underlining the danger of the sport. The Spaniard said: "On a day like this I don't know what to say. Marco, rest in peace."American Nicky Hayden, the 2006 champion who rides for Italian team Ducati, said: "It is a really horrible day for all of us."I saw Marco fall. Leaving the corner he lost the back end and probably he didn't manage to regain his balance on the bike. I feel really bad. On the track we are all brothers. Marco, we will miss you so much."British MotoGP rider Cal Crutchlow wrote on Twitter: "RIP Marco Simoncelli ! A great rider and all round nice guy. My thoughts are with all his family & friends. I will never forget today."And Formula One driver Mark Webber tweeted: "R.I.P Marco A special talent that will be missed... Thinking of your loved ones, and all the motogp paddock..mark."Italian Olympic Committee president Gianni Petrucci, said Sunday marked the saddest day of his presidency. "Life is sacred; you shouldn't die at age 24 just for a race," he said.Meanwhile Italian football giants Inter and AC Milan were among the first sports clubs to offer their commiserations - players wore black armbands and observed a minute's silence."AC Milan offers a hug to the family of Marco, a huge rossonero fan, and we want to offer the most sincere and heartfelt condolences in this sad moment," the club said on its website.An Inter Milan statement said the club "shares in the pain" of the entire sports world over the tragedy.

It was the 2nd bike that hit him. Hit his head & took his helmet. Not sure he would have survived even if his helmet stayed on. Not sure what their speeds were, but someones head vs a full speed bike hitting him even with the helmet.

Yes, was very sad to hear this news. I watch the MotoGP races along with the World Superbike races. I'm a Nicky fan, rooting for the Ducati's. That was awful to see him just laying there on the road, not moving. There's not too much you can do with the bikes from a safety standpoint, especially a helmet coming off.

RIP Marco, my thoughts and prayers are with you and your family

"The individual has always had to struggle to keep from being overwhelmed by the tribe" - Friedrich Nietzsche